1. Field of the Invention
The present invention relates to an interchangeable blade cutting tool in which a blade section is removably installed on a tool body.
2. Prior Art
An example of this kind of interchangeable blade cutting tool of the prior art consists of removably coupling a rear end section of a blade section having a cutting section at least equipped with one cutting blade, and a front end side portion of a bolt section having male threads, wherein together with this coupled blade section and bolt section being inserted into a mounting hole having female threads provided in a tool body, as a result of the male threads of the bolt section engaging with the female threads of the mounting hole, the blade section is removably installed by being drawn into the rear end side in the axial direction of the tool body.
For example, as shown in FIG. 34, an interchangeable blade cutting tool 10 is disclosed in Japanese Patent No. 2656949, as shown by its FIGS. 2 and 4. In this cutting tool 10, hook section 24 composed of groove 22 and flange 23 that opens extending in the lateral direction, is formed by cutting away the outer peripheral surface of tapered section 21 which is the rear end side of blade section 20, while hook section 34 composed of groove 32 and flange 33 and having a shape that corresponds to hook section 24 of blade section 20, is formed by cutting away the outer peripheral surface of tapered section 31 which is the front end side portion of bolt section 30, and blade section 20 and bolt section 30 are coupled by then mutually engaging these hook sections 24 and 34.
In addition, in the state in which blade section 20 is installed on tool body 11, the outer peripheral surface of tapered section 21 of blade section 20 presses against the inner peripheral surface of tapered hole 13 of mounting hole 12.
However, if blade section 20 and bolt section 30 are coupled by engaging hook sections 24 and 34 in this manner, although hook section 34 of bolt section 30 draws in blade section 20 towards the rear end side as a result of male threads 35 of bolt section 30 screwing into female threads 14 of mounting hole 12, there is the problem of tapered section 21 of blade section 20 being biased towards the opposite side of groove 22 of hook section 24 (direction indicated with a white arrow in the drawing) as a result of not following axis 0 of tool body 11, thereby causing blade section 20 to become eccentric with respect to axis 0 of tool body 11.
Moreover, since hook section 24 of blade section 20 is formed within tapered section 21, considerable bias also occurs in the force by which the outer peripheral surface of tapered section 21 of blade section 20 presses against the inner peripheral surface of tapered hole 13 of mounting hole 12, thereby causing the above tendency for blade section 20 to become eccentric to be more prominent.
Moreover, as an example of a different problem, in the state in which blade section 20 and bolt section 30 are removed from tool body 11, since the coupling between blade section 20 and bolt section 30 cannot be maintained, it is necessary to insert and screw in bolt section 30 into mounting hole 12 of tool body 11 in advance, thereby resulting in inferior workability.
In addition, an interchangeable blade cutting tool 40 as shown in FIG. 35 is also disclosed in Japanese Patent No. 2656949, as shown by its FIGS. 2 and 4. In this cutting tool 40, a hook section 54 in the shape of a dovetail (convex portion of the cross-section of a dove's tail) comprised of a pair of grooves 52 and a pair of flanges 53 that opens extending in the lateral direction, is formed in rear end section 51 of blade section 50, while a hook section 64 in the shape of a dovetail (concave portion of the cross-section of a dove's tail) comprised of a pair of grooves 62 and a pair of flanges 63 and having a shape corresponding to hook section 54 of blade section 50, is formed in front end side portion 61 of bolt section 60, and blade section 50 and bolt section 60 are coupled by mutually engaging these hook sections 54 and 64. (Furthermore, an interchangeable blade cutting tool having a similar constitution is also disclosed in European Patent Specification No. 0776719, as shown by its FIG. 1.)
However, in this interchangeable blade cutting tool 40, when blade section 50 is drawn into the rear end side in the direction of axis 0 by bolt section 60, a force acts so as to widen dovetail hook section 64 formed on the front end side portion of bolt section 60 (directions indicated with white arrows in the drawing), thereby causing deformation of this hook section 64 and making it difficult to maintain a stable installation state for blade section 50.
In addition, when installing blade section 50 in tool body 41, although blade section 50 and bolt section 60 are inserted into mounting hole 42 of tool body 41 after bolt section 60 and blade section 50 are coupled in the state of having been removed from tool body 41, since coupling between blade section 50 and bolt section 60 only takes place by means of the engaging of dovetail hook section 54 and dovetail hook section 64, there was the problem of the coupling of blade section 50 and bolt section 60 easily becoming disconnected.
Furthermore, as shown in FIG. 36, although an approach has been attempted for making the coupling between blade section 50 and bolt section 60 comparatively resistant to disconnection by increasing the length of male threads 65 of bolt section 60, and then screwing in bolt section 60 by a prescribed amount into mounting hole 42 of tool body 41 in advance, followed by coupling with blade section 50 and then screwing in male threads 65 of bolt section 60, when this is done, the amount of thread travel required to screw male threads 65 of bolt section 60 into female threads 44 of mounting hole 42 increases considerably, and the amount of turning required to turn blade section 50 coupled to bolt section 60 increases accompanying this, thereby preventing this approach from being an efficient means for solving the problem.
In addition, an interchangeable blade cutting tool like that shown in FIG. 37 is disclosed in UK Patent Specification No. 990353 (“UK '353”), as shown by its FIGS. 1 and 3, and an interchangeable blade cutting tool disclosed in UK Unexamined Patent Application, First Publication No. 2158374 (“UK '374”), as shown by its FIG. 5, although not shown in the drawings, are examples of being able to suppress the problem of eccentricity of the blade section as described above.
The interchangeable blade cutting tool as shown in FIG. 37 that is disclosed in UK '353, as shown by its FIGS. 1 and 3, has a hook section 84 opened in rear end surface 82 of blade section 80, and a hook section containment hole 85, which is continuous with the front end side of blade section 80 and is opened in outer peripheral surface 81 of rear end section 81, formed in rear end section 81 of blade section 80, while hook section 94, which is composed of rotationally symmetrical end section 92 and roughly cylindrical shaft section 93 that are able to pass through hook hole 84 and which have the axis of bolt section 90 as their two-fold axis, is formed in front end side portion 91 of bolt section 90.
When blade section 80 is installed on tool body 71, by suitably screwing in male threads 96 of bolt section 90 into female threads 73 of mounting hole 72, and by inserting blade section 80 towards the rear end side within mounting hole 72, end section 92 of bolt section 90 in hook section 94 is inserted into hook section containment hole 85 from hook hole 84.
Next, when blade section 80 is relatively turned by a prescribed angle towards the front in direction of screwing rotation S by which it is screwed into bolt section 90 (the direction of rotation when bolt section 90 is turned with respect to tool body 71 when male threads 96 of bolt section 90 are screwed into female threads 73 of mounting hole 72), as a result of rotational force transmission wall 95 formed on end section 92 of hook section 94 contacting edge 86 of the opening into outer peripheral surface 83 of hook section containment hole 85, the rotational force imparted from blade section 80 is transmitted to bolt section 90, and male threads 96 of bolt section 90 are screwed into female threads 73 of mounting hole 72.
When bolt section 90 is drawn into the rear end side, as a result of end section 92 of hook section 94 contacting and locking wall 87 surrounding hook hole 84, namely the wall that faces the front end side in hook section containment hole 85, the relative movement of blade section 80 and bolt section 90 in the direction in which they move away from each other in the axial direction is inhibited, causing blade section 80 and bolt section 90 to be coupled, and resulting in blade section 80 being drawn into the rear end side and removably installed.
Here, in an interchangeable blade cutting tool 70 as described above, in the state in which a blade section 80 is drawn into the rear end side and installed on tool body 71, in order to transmit rotational force imparted from blade section 80 when female threads 96 of bolt section 90 are screwed in to bolt section 90, rotational force transmission wall 95 formed on end section 92 of hook section 94 must contact edge 86 of the opening into outer peripheral surface 83 of hook section containment hole 85.
Whereupon, the prescribed angle at which blade section 80 is able to relatively rotate towards the front in direction of rotation S by screwing into bolt section 90 after end section 92 of hook section 94 is inserted into hook section containment hole 85 from hook hole 84 is restricted by a slight amount, and when bolt section 90 is drawn into the rear end side, it becomes difficult to secure a large enough surface for mutually contact between wall 87 surrounding hook hole 84 and end section 92 of hook section 94, thereby preventing the maintaining of a stable installation state for blade section 80.
In addition, since shaft section 93 of hook section 94 is simply formed roughly in the shape of a cylinder, it is unable to provide adequate rigidity, thereby making it difficult to maintain stable installation of blade section 80.
Moreover, when male threads 96 of bolt section 90 are attempted to be loosened from female threads 73 of mounting hole 72 in order to remove blade section 80 from tool body 71, unless blade section 80 is relatively rotated towards the rear in the direction of rotation S in which blade section 80 is screwed into bolt section 90 by the prescribed angle at which blade section 80 is relatively rotated towards the front in the direction of rotation S in which blade section 80 is screwed into bolt section 90, the rotational force imparted from blade section 80 cannot be transmitted to bolt section 90, resulting in the problem of poor workability due to the bother involved when removing blade section 80, as well as the risk of blade section 80 becoming disconnected from bolt section 90 in the case force is applied towards the rear in the direction of rotation S in which it is screwed into this bolt section 80 even if blade section 80 is installed on tool body 71.
In addition, in the interchangeable blade cutting tool like that disclosed in 4 UK '374, as shown by its FIG. 5, a hook section is formed in the rear end section of a blade section, and this hook section is roughly T-shaped when viewed from the side and is composed of a rotationally symmetrical end section and roughly cylindrical shaft section that use the axis of the blade section as their two-fold axis. As a result of screwing in the male threads of the bolt section into the female threads of a mounting hole in the tool body after inserting this hook section a hook section containment hole from a hook hole formed in a bolt section, the bolt section and blade section are drawn in towards the rear end side so as to maintain the state in which the blade section and bolt section are relatively rotated about 90°.
However, in this type of interchangeable blade cutting tool, since there is no impairment of relative rotation of the blade section and bolt section in the peripheral direction, not only during installation of the blade section but also after the blade section has been installed on the tool body, in the case a force in the peripheral direction is applied to the blade section, there is the risk of the blade section easily becoming disconnected from the bolt section, thereby resulting in the problem of an extremely poor installation state.
In addition, since the shaft section of the hook section is only formed into a roughly cylindrical shape, the problem remains in which it is unable to secure adequate rigidity.
In consideration of the above problems, the object of the present invention is to provide an interchangeable blade cutting tool and blade section installed thereon that eliminates the occurrence of eccentricity of the blade section and is able to maintain a stable installation state for the blade section.